Pathogenicity Differentiation And Molecular Variation Of Rice Stripe Virus

Tweenty-three isolates of Rice stripe virus (RSV) from Yunnan, Jiangsu, Shandong, Henan, and Anhui provinces were inoculated to rice varieties by landelphax striatellus.According to the morbidity, tweenty-three isolates could be divided into five grades, namely strong virus(sv), semi-strong virus(ss), middle strong virus(ms), weak virus(wv) and least weak virus(lw). Pathogenicity differentiation correlated with geographic distribution, strain differences and rice varieties. There were differences among isolates in the morbidity, time to exhibit disease, symptom and influences to landelphax striatellus's transmission.Two nature populations, Yunnan(YN) and out of Yunnan(OY), showed obvious different pathogenicity too. Some strong virus screened, more weak virus composed the population YN.Pupulation OY had more strong virus than YN and belong to mixed and variant population of five grades. The isolate of YBS07 showed stong pathogenicity similar to OY in the time to exhibit disease, symptom and influences to landelphax striatellus's transmission. The relationship between pathogenicity differentiation and epidemic of diseases suggested that specific measures should be taken in disease prevention and control.The genomes of eight representative isolates on pathogenicity were sequenced.Analysis of genetic variation showed that different fragment display different variant feature, that isolates of YN differed from isolates of OY in genetic relations obviously and that YBS07 isolate conducted genetic relations between YN and OY with trending to YN. Analysis of genetic diversity indicat that four weak isolates of YN were compressed by more negative selection pressure than the other four isolates of OY in RdRp,NS3,SP and NSvc4.The genetic diversity of YBS07 was between YN and OY with trending to YN.Analysis of population genetic distance display that the RSV population in china can divided into three subgroups,Yunnan subgroup,out of Yunnan subgroup, mixed subgroup originated from Yunnan group.There existed invasion between YN and OY. Analysis of population genetic diversity showed that seven genes of RSV were compressed strong negetive selection pressure with NS2>NS3>CP>NSvc2>SP>NSvc4>RdRp in genetic diversity and RdRp>NSvc4 >SP>NSvc2>CP>NS3>NS2 in conservation.The analysis of genetic diatance of IR4 also showed that there existed mixed subgroup and invasion between YN and OY.Three types of IR4 experienced two differentiations and two separations.Analysis of sequence showed that the terminal untrantion regions(UTR) of genome of RSV had hight conservation,with variation between YN an OY. The UTR could form stable hairpin structure.Analysis of amino acid sequence showed that RdRp had transmembrane segments, coiled coils and some protein functional sites such as short-chain dehydrogenases/reductases family signature.NS2 had a strong potential cleavage site of signal peptide.NSvc2 had an N-signal peptide, a strong potential cleavage site of signal peptide and the property of membrane protein. NS3 had a coiled coil, some protein functional sites, and a differences of C-terminal hydrophobicity between YN and OY.CP had a coiled coil and some protein functional sites. SP and NSvc4 both had a potential cleavage site of signal peptide,a transmembrane segment and somes protein functional sites.Analysis of stop codons indicated that RSV prefers to use UAG as the stop codon and there are differences on preference of stop codon between YN and OY. Analysis of sequence showed that IR2-4 had direct repeat fragments and inverted repeat fragments, those could formed stable hairpin structure. IR3 and IR4 even had obvious insert and missing sequences.A recombinant RNA of one isolate of Rice stripe virus(RSV) from Chuxiong(YCX07), Yunnan province, China, was sequenced. The RNA(YCX07R) was recombined from the 3' segments of RNA2 and RNA3 of RSV. The recombinant RNA uses ambisense coding strategy and encodes two proteins, namely YCX07R-5P and YCX07R-3P. The two proteins located on the 5' end of the plus and minus strand, respectively. This is similar to the four RNAs of RSV. It was discussed that the RNA was recombined from abortion replication or linked by two recombinant fragments through the recombinant site directly.